The present invention relates to an ignition timing control device for an internal combustion engine, and more particularly to a device which is designed to restrain knocking which tends to occur when the engine is manipulated in an attempt to produce an acceleration higher than a predetermined level.
It is known in the art that excessive knocking has an adverse effect on the durability of the engine whereas acceptable knocking contributes to attainment of optimum engine power output and fuel consumption characteristics. It is also known in the art that occurrence of knocking is closely related to the ignition timing of the engine and tends to be increased as the ignition timing is advanced.
In order to cope with the aforementioned situation, there has conventionally been proposed a device which is so designed as to normally maintain an acceptable knocking condition by causing the ignition timing to be advanced or retarded while detecting the knocking condition which is currently occurring in the engine, thereby achieving improved engine power output and fuel consumption characteristics.
In the conventional device described above, a feed-back control system is employed for controlling the ignition timing of the engine, so that a predetermined period of time, which corresponds to the time delay in response of the feed-back control system, is taken before the ignition timing is actually advanced or retarded in accordance with the detection of the current knocking condition. Thus, with such a device, it is possible to control the ignition timing to an optimum one in the case where the strength of knocking varies sufficiently slowly with respect to the predetermined period of time mentioned above.
Under a transitional driving condition where the driving condition is suddenly changed, however, there is the tendency that due to the time delay in response of the feed-back control system, the conventional device fails to control the ignition timing to an optimum one since under such a condition, the knocking condition is suddenly changed.
Knocking is more likely to occur under the transitional driving condition, particularly during the early stage of acceleration, as will be seen in FIG. 1. Such transient knocking only lasts for a period of time corresponding to several ignitions but is strong enough to impart an uncomfortable feeling to the driver. In order to restrain the transient knocking, it is required that the ignition timing be relatively greatly retarded as quickly as possible subsequent to the engine manipulation effected to achieve sudden acceleration such as sudden depression of the accelerator pedal. With the conventional device, however, it is not possible to attain such great and quick retardation of the ignition timing because of the fact that the device is usually arranged such that the ignition timing control is effected with a predetermined control speed to stabilize the control, more particularly, to prevent a hunting phenomenon from occurring in the control. This coupled with the afore-mentioned tendency, further enhances the tendency that the conventional device fails to achieve an optimum control of the ignition timing when a sudden acceleration is to be effected. Thus, with the conventional device, the combustion condition in the engine is deteriorated when such an acceleration as mentioned above is to be made, which leads to deterioration in the fuel consumption and power output characteristics of the engine.
Accordingly, it is an object of the present invention to provide a novel and improved ignition timing control device for an internal combustion engine, which is so designed as to avoid strong knocking which tends to occur when the engine is manipulated to produce an acceleration higher than a predetermined level, thereby establishing an optimum combustion condition in the engine.
According to an aspect of the present invention, there is provided an ignition timing control device for an internal combustion engine, comprising:
means for setting the normal ignition timing of the engine;
means responsive to occurrence of knocking in said engine for providing a first signal;
means responsive to a manipulation of the engine for achieving an acceleration higher than a predetermined acceleration level, for providing a second signal; and
means for determining the actual ignition timing of the engine, said means being adapted, responsive to said first signal, for setting the ignition timing for an optimum knocking condition, said means being also adapted, responsive to said second signal, for causing said ignition timing to be quickly retarded in accordance with said second signal to such an extent that excessive knocking tending to occur when said manipulation is made can be avoided, and for causing said normal ignition timing to be recovered immediately after the end of the retardation thereof.
According to another aspect of the present invention, there is provided an ignition timing control device for an internal combustion engine, comprising:
means for setting the normal ignition timing of the engine;
means responsive to a manipulation of the engine for achieving an acceleration higher than a predetermined acceleration level, for providing a first signal; and
means for determining the actual ignition timing of the engine, said means being adapted, responsive to said first signal, for causing said normal ignition timing to be quickly retarded in accordance with said first signal to such an extent that excessive knocking tending to occur when said manipulation is made can be avoided, and for causing said normal ignition timing to be recovered immediately after the end of the retardation thereof.